Room-Temperature Synthesis of the Highly Polar Cluster Compound Sn[SnCl][W3Cl13]

A new synthetic strategy is employed to synthesize a tungsten trinuclear cluster compound with an ionic liquid (IL) as the reaction medium. Dark brown block-shaped crystals of Sn[SnCl][W3Cl13] were obtained at room temperature by reacting tin and WCl6 in Lewis acidic ionic liquid [BMIM]Cl/AlCl3 ([BMIM](+) = 1-butyl-3-methylimidazolium). Compound Sn[SnCl][W3Cl13] crystallizes in the polar hexagonal space group P6(3) with cell parameters a = 959.8(1) and c = 1190.3(2) pm. The crystallographic point group of the [W-3(mu(3)-Cl)(mu-Cl)(3)Cl-9](3-) cluster anions is C-3, but C-3v pseudosymmetry is observed within twice the standard deviation of the bond lengths. The W-W bond length is 272.18(6) pm. The tin(II) cations, which are in trigonal pyramidal and in distorted trigonal-antiprismatic coordination spheres that comprise chloride ions, connect the clusters into layers that are stacked according to the 6(3) screw axis. One of the chloride ions is bound only to a single tin cation resulting in a [(SnCl)-Cl-II](+) group with a Sn-Cl bond length of 236.1(5) pm. The pronounced polarity of the crystal structure means that its diffraction pattern exhibits huge deviations from Friedel's law. Most remarkable is that the intensity (F-c(2)) of reflection 004 is 175% of the intensity of the 00 (4) over bar reflection.